This invention relates to a fuel injection system for a watercraft engine and more particularly to an improved fuel injection system for a personal watercraft.
As is well known, personal watercraft are a very popular type of watercraft and are utilized by many people. A personal watercraft generally is designed so as to be operated by a single rider who may carry one or a few additional passengers. Because of the small nature of these watercraft, at times the trim condition can vary significantly.
In order to provide a greater latitude of control for the watercraft and to accommodate for varying trim conditions, the jet propulsion unit, the type of propulsion unit commonly used in these watercraft, may be provided with a trim adjusting system whereby the trim may be adjusted through changing the angle of the discharge nozzle of the jet propulsion unit about a horizontal axis or in some other manner. This permits the rider more control over the watercraft trim condition especially during planing.
It has been proposed recently to employ fuel injection systems for personal watercraft. Fuel injection systems offer the opportunity of increased fuel economy and exhaust emission control as well as better overall engine performance. These systems employ generally a low pressure pump that delivers fuel to a high pressure pump which, in turn, then delivers the fuel to the fuel injectors of the engine. Normally, the fuel is supplied through a fuel rail and a pressure regulator is positioned in the fuel rail. The pressure regulator regulates the fuel pressure by dumping excess fuel back to the fuel tank or some other place upstream of the high pressure pump.
However, when the trim condition of a watercraft is changed, then the angular relationship of the fuel lines and the fuel rail can change. When this happens, then the pressure differences against which the pumps may act can vary and this can result in erratic or unstable engine operation.
It is, therefore, a principal object of this invention to provide an improved fuel supply system for a personal watercraft.
It is another object of this invention to provide an improved fuel supply system for a personal watercraft having a trim adjustment and wherein adjustment of the trim has a minimal effect on the injection system when adjustments are made.
With the fuel supply system and particularly the fuel rail, it is desirable to have the fuel rail disposed so that it extends at an angle to the horizontal so that the inlet side of the fuel supply system and the return are always in a condition wherein the slope is in an upward direction. That is, it is desirable to provide an arrangement wherein the fuel rail is disposed so that the pressure regulator is disposed at a higher level than the inlet side to the fuel rail. This condition should be maintained regardless of the trim adjustment.
In connection with the fuel system, it is also desirable to maintain the arrangement so that any fuel vapors which may be entrapped in the system can easily flow back on the return path. Thus, it is important to ensure that the fuel rail is always inclined in a generally upward direction from its inlet end to the outlet end that communicates back with the fuel tank. This will help to ensure that vapors will be purged and will not enter the fuel injectors and cause improper injection. It is, therefore, a still further object of this invention to provide a fuel rail arrangement for a watercraft and trim system therefor wherein that regardless of the trim angle during normal planing operation, the air will be purged from the fuel rail because the fuel rail is disposed so that it is always inclined upwardly from its supply end to its return end.